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Biomedical subjects

Andreas Bergmann

Publications and source records attributed to Andreas Bergmann.

At least 19 recordsLinked to original sources
PubMed2005

Proteolytic processing pattern of the endothelin-1 precursor in vivo.

Endothelin-1 (ET-1) is a potent vasoconstrictor, which has been implicated in diseases involving dysfunctions of the cardiovascular system. For the biogenesis of ET-1, a larger precursor peptide (proET-1) is cleaved at two sites to give rise to bigET-1, which is subsequently cleaved to generate mature ET-1. In the present study, we investigated, which other peptides are derived from proET-1 in vivo. Six sandwich immunoassays covering various regions of proET-1 were developed and used to detect circulating proET-1 immunoreactivities in plasma of healthy subjects and septic patients. With this approach we could (a) demonstrate that, in addition to bigET-1/ET-1, three stable proET-1 fragments are generated, (b) exclude two previously discussed regions as sites for prohormone conversion and (c) show that the proteolytic processing pattern of proET-1 is unchanged under pathological conditions, which are associated with elevated levels of proET-1 fragments. The high stability and similarity in concentration of the proET-1 fragments suggest that these might be non-functional in the circulation. Stable proET-1 fragments maybe used in the future as reliable diagnostic targets to indirectly assess the release of ET-1, which might help to more selectively direct therapeutic measures.

Endothelin-1↗
PubMed2005

Decreased serum amyloid beta(1-42) autoantibody levels in Alzheimer's disease, determined by a newly developed immuno-precipitation assay with radiolabeled amyloid beta(1-42) peptide.

BACKGROUND: Autoantibodies against amyloid beta (A beta) peptide found in patients with Alzheimer's disease (AD) also occur naturally in the general population independently of the cognitive status. METHODS: We compared serum A beta(1-42) autoantibody levels (A beta(1-42)-AL) of 96 AD patients and 30 healthy elderly control subjects (HC), assessing their diagnostic value for AD with a newly developed immunoprecipitation assay with radiolabeled A beta(1-42) peptide. RESULTS: We found a highly significant decrease of A beta(1-42)-AL in AD patients (p = .001) independently of age, cognitive status, and apolipoprotein E epsilon4 carrier status. Amyloid beta(1-42) autoantibody levels were correlated with gender in AD, with a higher level occurring in women. When A beta(1-42) autoantibody sensitivity (specificity) was set >80%, specificity (sensitivity) was below 50% to correctly allocate patients and healthy control subjects. CONCLUSIONS: Our data indicate a potentially pathophysiologic decrease of serum A beta(1-42) antibodies in AD. Amyloid beta(1-42) antibodies in the serum alone, however, seem not to be useful as a diagnostic marker of AD.

Aged↗
PubMed2005

The CARD-carrying caspase Dronc is essential for most, but not all, developmental cell death in Drosophila.

The initiator caspase Dronc is the only Drosophila caspase that contains a caspase activation and recruitment domain (CARD). Although Dronc has been implicated as an important effector of apoptosis, the genetic function of dronc in normal development is unclear because dronc mutants have not been available. In an EMS mutagenesis screen, we isolated four point mutations in dronc that recessively suppress the eye ablation phenotype caused by eye-specific overexpression of hid. Homozygous mutant dronc animals die during pupal stages; however, at a low frequency we obtained homozygous adult escapers. These escapers have additional cells in the eye and wings that are less transparent and slightly curved down. We determined that this is due to lack of apoptosis. Our analyses of dronc mutant embryos suggest that dronc is essential for most apoptotic cell death during Drosophila development, but they also imply the existence of a dronc-independent cell death pathway. We also constructed double mutant flies for dronc and the apoptosis inhibitor diap1. dronc mutants can rescue the ovarian degeneration phenotype caused by diap1 mutations, confirming that dronc acts genetically downstream of diap1.

Alleles↗
PubMed2005

Serum neopterin for early assessment of severity of severe acute respiratory syndrome.

Neopterin and C-reactive protein (CRP) concentrations were determined in serum samples from 129 severe acute respiratory syndrome (SARS) patients and 156 healthy blood donors. In the patients with confirmed SARS, an early neopterin elevation was detected already at the day of onset of symptoms and rose to a maximum level of 45.0 nmol/L 3 days after the onset. All SARS patients had elevated neopterin concentrations (>10 nmol/L) within 9 days after the onset. The mean neopterin concentrations were 34.2 nmol/L in acute sera of SARS patients, 5.1 nmol/L in convalescent sera, and 6.7 nmol/L in healthy controls. In contrast, the mean CRP concentrations in both acute and convalescent sera of SARS patients were in the normal range (<10 mg/L). Serum neopterin level in SARS patients was associated with fever period and thus the clinical progression of the disease, while there was no significant correlation between the CRP level and the fever period. Serum neopterin may allow early assessment of the severity of SARS. The decrease of neopterin level was found after steroid treatment, which indicates that blood samples should be collected before steroid treatment for the neopterin measurement.

Adrenal Cortex Hormones↗
PubMed2005

Copeptin, a stable peptide derived from the vasopressin precursor, is elevated in serum of sepsis patients.

Vasopressin is one of the key regulators of the body's water and solute balance. When this balance is pathologically disturbed, determination of serum vasopressin concentrations might be a helpful tool for guiding therapy. However, due to its instability and considerable association to platelets, reliable measurement of circulating vasopressin is difficult to achieve, if at all. In search of a more robust way for quantifying vasopressin release, we identified copeptin, a glycopeptide with unknown function, as an alternative diagnostic target. Since copeptin is derived from the same precursor peptide as vasopressin, released amounts of copeptin should mirror those of vasopressin. With a newly developed sensitive sandwich immunoassay, we detected strongly elevated concentrations of fully processed copeptin in serum of septic shock patients. The magnitude of elevation and the high stability of copeptin in serum and plasma indicate that copeptin measurement is not affected by the problems, which are associated with the direct measurement of vasopressin, and thus is apparently suitable to indirectly determine the release of vasopressin.

Enzyme-Linked Immunosorbent Assay↗
PubMed2005

Genetic control of programmed cell death in Drosophila melanogaster.

Apoptosis is a genetically controlled form of cell death that is an important feature of animal development and homeostasis. The genes involved in the control and execution of apoptosis are conserved throughout evolution. However, the actual molecular mechanisms used by these genes vary from species to species. In this review, we focus on the genetic components of apoptosis in the fruit fly Drosophila melanogaster, and compare their mode of action to the one employed by the homologous genes in mammals. We also cover recent advances that show that apoptotic genes have a requirement in processes other than apoptosis.

Animals↗
PubMed2005

Release of the mitochondrial enzyme carbamoyl phosphate synthase under septic conditions.

To identify sepsis-related dysregulations of protein expression in the liver, we used a baboon model of acute endotoxemia and performed comparative proteome analysis. Treatment with lipopolysaccharide (LPS) was followed by an early but long-lasting (5-48 h) generation of N-terminal fragments of carbamoyl phosphate synthase-1 (CPS-1), an abundant enzyme of the hepatic urea cycle, which is normally located in the mitochondrial matrix. In addition, we developed a new sandwich immunoassay to determine circulating CPS-1 in human and baboons. We found CPS-1 to be induced by LPS and to be released into the circulation of healthy humans and baboons as early as 4 to 5 h after stimulation. Similarly, CPS-1 levels increased after injection of gram-positive bacteria in another baboon model. Enhanced CPS-1 levels were also detected in serum of patients with sepsis. Our data demonstrate fragmentation of CPS-1 in the liver and early increase in circulating CPS-1 levels under septic conditions. We suggest that circulating CPS-1 might serve as a novel serum marker indicating mitochondrial impairment of the liver and/or the small intestine in critically ill patients.

Animals↗
PubMed2004

Pro-atrial natriuretic peptide is a prognostic marker in sepsis, similar to the APACHE II score: an observational study.

INTRODUCTION: Additional biomarkers in sepsis are needed to tackle the challenges of determining prognosis and optimizing selection of high-risk patients for application of therapy. In the present study, conducted in a cohort of medical intensive care unit patients, our aim was to compare the prognostic value of mid-regional pro-atrial natriuretic peptide (ANP) levels with those of other biomarkers and physiological scores. METHODS: Blood samples obtained in a prospective observational study conducted in 101 consecutive critically ill patients admitted to the intensive care unit were analyzed. The prognostic value of pro-ANP levels was compared with that of the Acute Physiology and Chronic Health Evaluation (APACHE) II score and with those of various biomarkers (i.e. C-reactive protein, IL-6 and procalcitonin). Mid-regional pro-ANP was detected in EDTA plasma from all patients using a new sandwich immunoassay. RESULTS: On admission, 53 patients had sepsis, severe sepsis, or septic shock, and 68 had systemic inflammatory response syndrome. The median pro-ANP value in the survivors was 194 pmol/l (range 20-2000 pmol/l), which was significantly lower than in the nonsurvivors (median 853.0 pmol/l, range 100-2000 pmol/l; P < 0.001). On the day of admission, pro-ANP levels, but not levels of other biomarkers, were significantly higher in non-surviving [corrected] than in surviving [corrected] sepsis patients (P = 0.001). In a receiver operating characteristic curve analysis for the survival of patients with sepsis, the area under the curve (AUC) for pro-ANP was 0.88, which was significantly greater than the AUCs for procalcitonin and C-reactive protein, and similar to the AUC for the APACHE II score. CONCLUSION: Pro-ANP appears to be a valuable tool for individual risk assessment in sepsis patients and for stratification of high-risk patients in future intervention trials. Further studies are needed to validate our results.

APACHE↗
PubMed2004

Identification of an Adrenomedullin precursor fragment in plasma of sepsis patients.

Adrenomedullin and PAMP are potent vasodilatory peptides derived from a common larger precursor peptide. Elevation of circulating levels of both peptides has been described for diseases involving dysfunction of the cardiovascular system. However, the reliable quantification has been hampered by their short half-life times and - as known for Adrenomedullin -- the existence of a binding protein. Here we report the identification of another peptide derived from the Adrenomedullin precursor, termed proADM 45-92, which is present in large concentrations in plasma of septic shock patients. This peptide is produced in stoichiometric amounts to Adrenomedullin and PAMP, but -- contrary to them -- is apparently non-functional and stable. Thus, proADM 45-92 represents a suitable diagnostic target which could be used to assess the concentrations of Adrenomedullin gene products released into the bloodstream.

Adrenomedullin↗
PubMed2004

A coated tube assay for the detection of blocking thyrotropin receptor autoantibodies.

We developed a coated tube assay to discriminate TSH-receptor-stimulating autoantibodies [thyroid-stimulating antibodies (TSAb)] from those autoantibodies blocking TSH binding without intrinsic activation [thyroid-blocking antibodies (TBAb)]. The wild-type TSH receptor in the TSH binding-inhibitory assay was exchanged for a chimeric receptor where a TSAb epitope (amino acids 8-165) was replaced by comparable LH-R residues. Binding of (125)I-labeled TSH to this chimera could be inhibited by sera containing TBAb up to 95%. Sera from 316 patients with Graves' disease and 17 with autoimmune thyroid disease were grouped according to their bioassay activity. At the decision threshold, the chimera A assay had a sensitivity of 78.0% for TBAb with a specificity of 90.2%. In detail, 19 of 22 (86.4%) TBAb sera and 15 of 23 (65.2%) TSAb/TBAb sera were positive but only 32 of 216 (14.0%) TSAb sera and 5 of 72 (6.9%) bioassay negative sera. There was a weak but significant positive correlation (r = 0.46) between the chimera assay and the bioassay for TBAb. This is the first report of a coated tube assay for the determination of TBAb employing an adaptation of the TSH binding-inhibitory format, which could be a useful alternative to the bioassay.

Animals↗
PubMed2003

Affinity purification and diagnostic use of TSH receptor autoantibodies from human serum.

Purification of TSH receptor autoantibodies (TRAb) from the serum of patients with Graves' disease (GD) might help to elucidate the nature of these disease causing autoantibodies. We describe here for the first time the successful affinity purification of human TRAb. Affinity purification was performed in a four step procedure with human recombinant TSH receptor (TSH-R) expressed in K562 cells. Purification from six different serum pools from patients with GD and two individual sera (one with only thyroid stimulating antibodies (TSAb) one with only thyroid blocking antibodies (TBAb)) resulted in a purity of 39.2+/-3.8 IU/mg TRAb or 25.7+/-2.1 microg IgG/IU (about 3.5-13.7 microg TRAb/ml serum). The average enrichment based on the respective original serum was 3420-fold (range 1200-10,000). The kDa of the purified TRAb were in the range of 0.7-2.6 x 10(-10)M. All purified TRAb (except from the TBAb serum which showed blocking activity) showed a more than 1000-fold stronger stimulation in the TSAb bioassay based on the IgG content than the original serum, and similar stimulation based on international units (IU/l) TRAb. When labelled purified TRAb were used in a competitive assay as tracer instead of bovine TSH, their binding to the human recombinant TSH-R on tubes was displaced by 99 of 100 GD sera (selected for TBII activity). Correlation to the standard TSH tracer was r=0.92. Interestingly, the use of TRAb tracer derived from a patient with TSAb and a patient with TBAb gave virtually identical results (r=0.93) with these patients, suggesting similar if not identical binding sites for both TRAb subtypes. In conclusion, this is the first report on the purification of human TRAb from the serum of patients with GD. The purified TRAb are of low concentration with high affinity, strong TBII and TSAb activity. Further characterisation may allow new insights in TRAb epitope localisation, the pathology of GD and the differences between TSAb and TBAb. Also, their use as tracer in a competitive assay is the first report on a completely homogenous assay with high sensitivity for TSH-R autoantibodies.

Animals↗
PubMed2003

Drosophila mixed lineage kinase/slipper, a missing biochemical link in Drosophila JNK signaling.

Mixed lineage kinases (MLKs) belong to the family of mitogen activated protein kinase kinase kinase (MAPKKK) and cause neuronal cell death mediated through c-Jun, N-terminal kinase (JNK) pathway. Recently, genetic studies in Drosophila revealed the presence of an MLK termed slipper (slpr). However, its biochemical features like physiological substrate, role in different MAPK pathways and developmental and tissue-specific expression pattern were not reported. Here, we report cDNA cloning, expression analysis and biochemical characterization of a Drosophila mixed lineage kinase (dMLK) that is also known as slipper. The protein structure analysis of dMLK/slipper revealed, in addition to the conserved domains, a stretch of glutamine in the amino terminus and an asparagine-threonine stretch at the carboxy-terminus. In situ hybridization and reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed that dMLK is expressed in early embryonic stages, adult brain and thorax. Ectopic expression of dMLK either in Drosophila S2 or in mammalian HEK293 cells leads to activation of JNK, p38 and extracellular signal regulated kinase (ERK) pathways. Further, dMLK directly phosphorylates Hep, dMKK4 and also their mammalian counterparts, MKK7 and SEK1, in an in vitro kinase assay. Taken together, our results provide for the first time a comprehensive expression profile and new biochemical insight of dMLK/slipper.

Animals↗
PubMed2003

Regulators of IAP function: coming to grips with the grim reaper.

Inhibitor of apoptosis proteins (IAPs) are a conserved class of proteins that control apoptosis in both vertebrates and invertebrates. They exert their anti-apoptotic function through inhibition of caspases, the principal executioners of apoptotic cell death. Recent advances in vertebrates and Drosophila have demonstrated that IAPs use ubiquitin conjugation to control the stability, and thus the activity, of select target proteins. The Drosophila IAP1 gene is an instructive example: it employs at least two distinct ubiquitin-dependent mechanisms of protein destruction. The apoptosis-inducing genes grim, reaper and hid modulate these mechanisms, and determine the outcome.

Animals↗
PubMed2003

HIDden targets of microRNAs for growth control.

How is the size of an animal determined? Why is it that humans grow larger than mice? Certainly, one of the most astonishing features of animal development is that every animal of a given species, and its organs and appendages, grow to approximately the same size. Surprisingly little is known about the biology of tissue growth and size control. Recent advances in Drosophila research have implicated a microRNA as an important regulator of animal size. These studies reveal an unexpected layer of size regulation in higher animals.

Animals↗
PubMed2002

Decrease of serum dipeptidylpeptidase activity in severe sepsis patients: relationship to procalcitonin.

A significant decrease of DPP IV activity has been found in patients with severe sepsis in relationship to the increase of procalcitonin. These findings might be explained by the high concentration of other substrates for DPP IV present in these patients. It can be hypothesized that this enzymatic decrease is bound to some changes in immunomodulation. Further studies will be necessary to elucidate the clinical importance of these findings.

Calcitonin↗
PubMed2002

Activation of the Drosophila MLK by ceramide reveals TNF-alpha and ceramide as agonists of mammalian MLK3.

Mixed lineage kinases (MLKs) are MAPKKK members that activate JNK and reportedly lead to cell death. However, the agonist(s) that regulate MLK activity remain unknown. Here, we demonstrate ceramide as the activator of Drosophila MLK (dMLK) and identify ceramide and TNF-alpha as agonists of mammalian MLK3. dMLK and MLK3 are activated by a ceramide analog and bacterial sphingomyelinase in vivo, whereas a low nanomolar concentration of natural ceramide activates them in vitro. Specific inhibition of dMLK and MLK3 significantly attenuates activation of JNK by ceramide in vivo without affecting ceramide-induced p38 or ERK activation. In addition, TNF-alpha also activates MLK3 and evidently leads to JNK activation in vivo. Thus, the ceramide serves as a common agonist of dMLK and MLK3, and MLK3 contributes to JNK activation induced by TNF-alpha.

Animals↗
PubMed2002

Regulation of cell number by MAPK-dependent control of apoptosis: a mechanism for trophic survival signaling.

Trophic mechanisms in which neighboring cells mutually control their survival by secreting extracellular factors play an important role in determining cell number. However, how trophic signaling suppresses cell death is still poorly understood. We now show that the survival of a subset of midline glia cells in Drosophila depends upon direct suppression of the proapoptotic protein HID via the EGF receptor/RAS/MAPK pathway. The TGFalpha-like ligand SPITZ is activated in the neurons, and glial cells compete for limited amounts of secreted SPITZ to survive. In midline glia that fail to activate the EGFR pathway, HID induces apoptosis by blocking a caspase inhibitor, Diap1. Therefore, a direct pathway linking a specific extracellular survival factor with a caspase-based death program has been established.

Animals↗